drm/i915: Use drm_i915_private directly from debugfs

The void *data passed to debugfs callbacks is actually the
drm_i915_private pointer, so use it thusly and avoid the to_i915(dev)
indirection.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170407194220.821-1-chris@chris-wilson.co.ukReviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -2568,8 +2568,7 @@ static int i915_guc_log_dump(struct seq_file *m, void *data)
 
 static int i915_guc_log_control_get(void *data, u64 *val)
 {
-	struct drm_device *dev = data;
-	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct drm_i915_private *dev_priv = data;
 
 	if (!dev_priv->guc.log.vma)
 		return -EINVAL;
@@ -2581,14 +2580,13 @@ static int i915_guc_log_control_get(void *data, u64 *val)
 
 static int i915_guc_log_control_set(void *data, u64 val)
 {
-	struct drm_device *dev = data;
-	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct drm_i915_private *dev_priv = data;
 	int ret;
 
 	if (!dev_priv->guc.log.vma)
 		return -EINVAL;
 
-	ret = mutex_lock_interruptible(&dev->struct_mutex);
+	ret = mutex_lock_interruptible(&dev_priv->drm.struct_mutex);
 	if (ret)
 		return ret;
 
@@ -2596,7 +2594,7 @@ static int i915_guc_log_control_set(void *data, u64 val)
 	ret = i915_guc_log_control(dev_priv, val);
 	intel_runtime_pm_put(dev_priv);
 
-	mutex_unlock(&dev->struct_mutex);
+	mutex_unlock(&dev_priv->drm.struct_mutex);
 	return ret;
 }